Hubbard Brook Ecosystem Study Research Articles

A century of change: Reconstructing the biogeochemical history of Hubbard Brook

AbstractEcosystems constantly adjust to altered biogeochemical inputs, changes in vegetation and climate, and previous physical disturbances. Such disturbances create overlapping ‘biogeochemical legacies’ affecting modern nutrient mass balances. To understand how ‘legacies’ affected watershed‐ecosystem (WEC) biogeochemistry during five decades of studies within the Hubbard Brook Experimental Forest (HBEF), we extended biogeochemical trends and hydrologic fluxes back to 1900 to provide an historical framework for our long‐term studies. This reconstruction showed acid rain peaking at HBEF in the late 1960s‐early 1970s near the beginning of the Hubbard Brook Ecosystem Study (HBES). The long‐term, parabolic arc in acid inputs to HBEF generated a corresponding arc in the ionic strength of stream water, with acid inputs generating increased losses of H+ and soil base cations between 1963 and 1969 and then decreased losses after 1970. Nitrate release after disturbance is coupled with previous N‐deposition and storage, biological uptake, and hydrology. Sulfur was stored in soils from decades of acid deposition but is now nearly depleted. Total exports of base cations from the soil exchange pool represent one of the largest disturbances to forest and associated aquatic ecosystems at the HBEF since the Pleistocene glaciation. Because precipitation inputs of base cations currently are extremely small, such losses can only be replaced through the slow process of mineral weathering. Thus, the chemistry of stream water is extremely dilute and likely to become even more dilute than pre‐Industrial Revolution estimates. The importance of calculating chemical fluxes is clearly demonstrated in reconstruction of acid rain impacts during the pre‐measurement period. The aggregate impact of acid rain on WEC exports is far larger than historical forest harvest effects, and even larger than the most severe deforestation experiment (Watershed 2) at HBEF. A century of acid rain had a calcium stripping impact equivalent to two W2 experiments involving complete deforestation and herbicide applications.

Watershed studies at the Hubbard Brook Experimental Forest: Building on a long legacy of research with new approaches and sources of data

AbstractThe Hubbard Brook Experimental Forest (HBEF) was established in 1955 by the U.S. Department of Agriculture, Forest Service out of concerns about the effects of logging increasing flooding and erosion. To address this issue, within the HBEF hydrological and micrometeorological monitoring was initiated in small watersheds designated for harvesting experiments. The Hubbard Brook Ecosystem Study (HBES) originated in 1963, with the idea of using the small watershed approach to study element fluxes and cycling and the response of forest ecosystems to disturbances, such as forest management practices and air pollution. Early evidence of acid rain was documented at the HBEF and research by scientists at the site helped shape acid rain mitigation policies. New lines of investigation at the HBEF have built on the long legacy of watershed research resulting in a shift from comparing inputs and outputs and quantifying pools and fluxes to a more mechanistic understanding of ecosystem processes within watersheds. For example, hydropedological studies have shed light on linkages between hydrologic flow paths and soil development that provide valuable perspective for managing forests and understanding stream water quality. New high frequency in situ stream chemistry sensors are providing insights about extreme events and diurnal patterns that were indiscernible with traditional weekly sampling. Additionally, tools are being developed for visual and auditory data exploration and discovery by a broad audience. Given the unprecedented environmental change that is occurring, data from the small watersheds at the HBEF are more relevant now than ever and will continue to serve as a basis for sound environmental decision‐making.

Fifty years of continuous precipitation and stream chemistry data from the Hubbard Brook ecosystem study (1963-2013).

The Hubbard Brook Ecosystem Study officially began on 1 June 1963. This archive contains the results of 50yr of collection and analysis of (at least) weekly stream water and precipitation samples obtained during the period 1963-2014 (from 1 June 1963 to 30 May 2013). Stream chemistry for the nine gauged watersheds and precipitation chemistry for precipitation gauges distributed throughout the Hubbard Brook Experimental Forest are reported as concentrations in (mg/L).

Climate change decreases nitrogen pools and mineralization rates in northern hardwood forests

AbstractNitrogen (N) supply often limits the productivity of temperate forests and is regulated by a complex mix of biological and climatic drivers. In excess, N is linked to a variety of soil, water, and air pollution issues. Here, we use results from an elevation gradient study and historical data from the long‐term Hubbard Brook Ecosystem Study (New Hampshire,USA) to examine relationships between changes in climate, especially during winter, and N supply to northern hardwood forest ecosystems. Low elevation plots with less snow, more soil freezing, and more freeze/thaw cycles supported lower rates of N mineralization than high elevation plots, despite having higher soil temperatures and no consistent differences in soil moisture during the growing season. These results are consistent with historical analyses showing decreases in rates of soil N mineralization and inorganic N concentrations since 1973 that are correlated with long‐term increases in mean annual temperature, decreases in annual snow accumulation, and a increases in the number of winter thawing degree days. This evidence suggests that changing climate may be driving decreases in the availability of a key nutrient in northern hardwood forests, which could decrease ecosystem production but have positive effects on environmental consequences of excess N.

The promise and peril of intensive-site-based ecological research: insights from the Hubbard Brook ecosystem study.

Ecological research is increasingly concentrated at particular locations or sites. This trend reflects a variety of advantages of intensive, site-based research, but also raises important questions about the nature of such spatially delimited research: how well does site based research represent broader areas, and does it constrain scientific discovery? We provide an overview of these issues with a particular focus on one prominent intensive research site: the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA. Among the key features of intensive sites are: long-term, archived data sets that provide a context for new discoveries and the elucidation of ecological mechanisms; the capacity to constrain inputs and parameters, and to validate models of complex ecological processes; and the intellectual cross-fertilization among disciplines in ecological and environmental sciences. The feasibility of scaling up ecological observations from intensive sites depends upon both the phenomenon of interest and the characteristics of the site. An evaluation of deviation metrics for the HBEF illustrates that, in some respects, including sensitivity and recovery of streams and trees from acid deposition, this site is representative of the Northern Forest region, of which HBEF is a part. However, the mountainous terrain and lack of significant agricultural legacy make the HBEF among the least disturbed sites in the Northern Forest region. Its relatively cool, wet climate contributes to high stream flow compared to other sites. These similarities and differences between the HBEF and the region can profoundly influence ecological patterns and processes and potentially limit the generality of observations at this and other intensive sites. Indeed, the difficulty of scaling up may be greatest for ecological phenomena that are sensitive to historical disturbance and that exhibit the greatest spatiotemporal variation, such as denitrification in soils and the dynamics of bird communities. Our research shows that end member sites for some processes often provide important insights into the behavior of inherently heterogeneous ecological processes. In the current era of rapid environmental and biological change, key ecological responses at intensive sites will reflect both specific local drivers and regional trends.

The Hubbard Brook Ecosystem Study: Celebrating 50 Years

Continuous, truly long-term studies are exceedingly rare in ecology. On 1 June 2013, the Hubbard Brook Ecosystem Study (HBES), located in the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, celebrated its 50th anniversary. This momentous event was fêted on 9 July with a day-long symposium at the research site. The site is administered by the USDA Forest Service and currently serves as NSF LTER and LTREB sites. The HBES was initiated in 1963 by F. H. Bormann, G. E. Likens, R. S. Pierce, and N. M. Johnson to study the ecological, hydrological, and biogeochemical interactions in watershed–ecosystems. The hallmark HBES small watershed–ecosystem approach has been replicated in many places throughout the world. During the past 50 years, the HBES has been highly productive and greatly expanded in scope. Six major scientific findings are especially noteworthy: (1) discovery of acid rain in North America and its impact on aquatic and terrestrial ecosystems (Likens et al. 1972, Likens and Bormann 1974); (2) validation of the small watershed–ecosystem approach as a powerful scientific tool in tackling problems at the landscape scale of complexity (ecological, hydrological, biogeochemical); (3) confirmation that clear-cutting and other major forest disturbances cause severe disruptions in the vital nitrogen cycle of terrestrial ecosystems (Likens et al. 1970); (4) major depletion of base cations, primarily calcium, from soil pools by acid rain (Likens et al. 1996); (5) dramatic decreases in chemistry of precipitation and stream water to extremely low concentrations (Likens and Buso 2012); and (6) that food limitation, climate, and forest structure account for most dramatic changes in the abundances of neotropical migrant birds (Holmes 2011). More than 1470 scientific publications, 11 books, and 8 monographs have been published. Hundreds of graduate, undergraduate, postdoctoral associates, and technicians have been mentored and trained at Hubbard Brook, resulting in 101 Ph.D. and 68 Master's theses. Some 40–50 investigators from 20 or more institutions currently do research at the Hubbard Brook Experimental Forest. The initial paper describing the conceptual approach and major objectives of the HBES was published in Science (Bormann and Likens 1967). Now, faced with greatly increasing problems of human-accelerated environmental change (Likens 1991), the Hubbard Brook approach to understanding complicated ecosystem function, and particularly the response to anthropogenic disturbances, is more valuable than ever. Gene E. Likens, Co-founder of the Hubbard Brook Ecosystem Study, is Founding Director, President Emeritus, and Distinguished Senior Scientist Emeritus of the Cary Institute of Ecosystem Studies.

Resolution of Respect: F. Herbert Bormann 1922–2012

Resolution of Respect: F. Herbert Bormann 1922–2012

SOME PERSPECTIVES ON LONG-TERM BIOGEOCHEMICAL RESEARCH FROM THE HUBBARD BROOK ECOSYSTEM STUDY

Integrated, long-term, ecological, hydrological, and biogeochemical studies have been done at the Hubbard Brook Experimental Forest since 1963 using the small watershed–ecosystem approach. Some biogeochemical results from these long-term studies, collectively called the Hubbard Brook Ecosystem Study, are described here, including approaches used for managing this large and complicated project. Some major biogeochemical findings of the Hubbard Brook Ecosystem Study are discussed briefly, including acid rain, and some biogeochemical research questions, opportunities, and challenges for the future are identified, including a recent whole-watershed addition of calcium silicate, weathering processes, and long-term trends in stream-water nitrate concentrations.

Nor Gloom of Night: A New Conceptual Model for the Hubbard Brook Ecosystem Study

Abstract The great challenge now facing forest ecosystem scientists and managers is to address the need for multiple ecosystem services over relatively large spatial and temporal scales (e.g., whole national forests over 50- to 100-year time frames). Here we present a new conceptual model for the study of forest ecosystems that aids in the analysis of factors that influence ecosystem structure, function, and services. We then go on to show how this model has been applied to the long-term Hubbard Brook Ecosystem Study. Our new model has three main components: (1) controllers, (2) ecosystem pattern and process, and (3) ecosystem functions and services. The controllers are the factors that drive ecosystem pattern and process; we split them into two groups, state factors and variable–stochastic factors. This new model will help to ensure a comprehensive approach to forest ecosystem analysis and will facilitate interactions of research with policy and management at many locations.

Ecologists and environmental politics: a history of contemporary ecology

Ecologists, like other scientist, have for decades debated their role in society. While some have argued that ecologists should participate in environmental politics, others have focused their attention strictly on scientific issues. In this book, Stephen Bocking explores the context of this debate by recounting the history of ecology in Great Britain, the United States, and Canada since the 1940s. Bocking tells this history through four case studies: the origins and early research of the nature conservancy in Great Britain; the development of ecology at the Oak Ridge National Laboratory in Tennesee; the work of the Hubbard Brook ecosystem study in New Hampshire; and research in fisheries ecology at the University of Toronto and the Ontario provincial government in Canada. In each institution, ecologists influenced the development of their discipline, and Bocking explains their work. By comparing these case studies, Bocking demonstrates how the places of contemporary science - laboratories, landscapes, and funding agencies - and its purposes, as expressed through the political roles of expertise and specific managerial and regulatory responsibilities, have shaped contemporary ecology and its application to pressing environmental problems.

ECOLOGY: A Personal History

[Figure: see text] ▪ Abstract FH Bormann, based on personal experience, recalls 55 years of association with the field of ecology, including the forces that led him into the field, research, development of the Hubbard Brook Ecosystem Study, and clashes between ecology, policy, and politics. He concludes with thoughts on humankind's search for the quality of life and sustainability.

Soil processes and sulfate loss at the Hubbard Brook Experimental Forest

The Hubbard Brook Ecosystem Study was designed to evaluate element flux and cycling in a northern hardwood forest and the effects of disturbance on these processes. In the original experiment, an entire watershed was deforested and regrowth was inhibited for three years using herbicides. Initial effects of the treatment included: elevated stream discharge, large increases in streamwater solute concentrations and elevated losses of those ions from the watershed. In contrast, streamwater concentrations and net ecosystem output of sulfate decreased in response to the treatment. During the post treatment period, the concentrations of most dissolved ions declined relative to a reference watershed while, again in contrast, sulfate concentrations increased relative to the reference. In this paper we develop a hypothesis which links acidification and sulfate adsorption processes in the soil to explain the observed trends in sulfate losses from the Hubbard Brook Experimental Forest.

Comment on Local Source Impacts at Hubbard Brook, New Hampshire

Information was presented that implied the Hubbard Brook Ecosystem Study precipitation chemistry data base may have been compromised by the presence of a small paper-making facility some 10 km to the north at Lincoln, New Hampshire. The plant operated on coal until 1969, intermittently until 1972, and then converted to oil in 1975. The article by Coffey stated the impact (of the plant) upon the site would tend to mask the effects of regional sulfur dioxide reductions. This note examines this charge. This author computed SO/sub 2/ concentration from ground level and elevated, stack level. It was concluded that this data indicated that any influences of local pollution sources on the Hubbard Brook precipitation chemistry are quite minimal, as indicated by both theoretical analysis of the source characteristics and statistical analysis of the precipitation chemistry record per se. Although there are substantial year to year variations, a large portion of the sulfate variance is explained by variations in seasonality and precipitation. The balance is due to meteorological variability and emission variations, but there is no firm statistical evidence as to which source or group of sources is influencing Hubbard Brook precipitation chemistry. This inquiry, in response to Coffey's allegation, hasmore » shown the necessity for understanding local source effects on precipitation chemistry as a prerequisite to full understanding and interpretation of monitoring data. 13 references, 1 table.« less

Pattern and Process in a Forested Ecosystem: Disturbance, Development and the Steady State based on the Hubbard Brook Ecosystem Study, by F. H. Bormann & G. E. Likens. Springer-Verlag, Berlin–Heidelberg–New York: xi + 253 pp, illustr., 24×16 ×2 cm, DM. 42 (or US$23.10). 1979.

Pattern and Process in a Forested Ecosystem: Disturbance, Development and the Steady State based on the Hubbard Brook Ecosystem Study, by F. H. Bormann & G. E. Likens. Springer-Verlag, Berlin–Heidelberg–New York: xi + 253 pp, illustr., 24×16 ×2 cm, DM. 42 (or US$23.10). 1979. - Volume 8 Issue 4

Forest ecosystem

Pattern and Process in a Forested Ecosystem: Disturbance, Development and the Steady State Based on the Hubbard Brook Ecosystem Study. By F.H. Bormann and G.E. Likens. Pp.253. (Springer: Berlin, Heidelberg and New York, 1979.) DM42, $23.10.

Predicting the effects of different harvesting regimes on forest floor dynamics in northern hardwoods

The effects of different intensities of forest management on forest floor organic matter and nitrogen dynamics in northern hardwoods were simulated with a computer model built from the extensive data base of the Hubbard Brook Ecosystem Study. Three cutting intensities and three rotation lengths were tested. In all cases, both nitrogen availability and forest floor organic matter declined for 15–30 years following cutting and required 60–80 years to recover to precut levels. Rotation length had a much greater effect on the forest floor than harvesting intensity with short-rotation (30-year) complete forest harvesting causing the greatest reduction in both biomass and nitrogen availability. Average forest floor biomass under this treatment was reduced to roughly one-half of that under clear-cutting (90-year rotation).

Some Ecological Consequences of a Computer Model of Forest Growth

The complexity of a forest ecosystem makes difficult any attempt to synthesize knowledge about forest dynamics or to perceive the implications of information and assumptions regarding forest growth. Although digital computer simulation seems to offer a potential for creating a complete model of forest growth, little progress has been reported. Computer simulation has been carried out for the growth of trees in even-aged stands of a single species (Mitchell 1969), and for meteorological energy exchange in a forest canopy (Waggoner & Reifsnyder 1968). A specific simulation built directly from Hubbard Brook data has been reported (Siccama et al. 1969). Successional change in northern hardwood forests has been predicted from observed birth and death rates (Leak 1970). A conceptual model has been created for the growth of individual tree seedlings from rates of photosynthesis and the distribution of photosynthates (Ledig 1969). Computer simulation has been carried out for some aspects in a few other terrestrial ecosystems, such as productivity in a corn crop (Duncan et al. 1967); but apparently no one has successfully reproduced the major characteristics of a mixed-species, mixed-aged forest from a conceptual basis. A computer simulation of forest growth is now developed that successfully reproduces the population dynamics of the trees in a mixed-species forest of north-east North America. The simulator is designed to be used in the Hubbard Brook Ecosystem Study and to provide output in the same form as the original vegetation survey of that study (Bormann et al. 1970). However, the underlying concepts of the simulation are general. The properties of each species are derived from its entire geographic range and in theory any non-hydrophytic species whose relevant characteristics are known can be entered into the simulation. In the present version of the program, the description of the environment is restricted to those features that have been recorded for the Hubbard Brook Forest, but the relative importance attached to each environmental factor has been influenced by the environmental characteristics of the north-eastern United States. It is hoped that a wide dissemination of this simulator will encourage others to test this version with their data and hence lead to later versions of wider usefulness and applicability. The basic goal was to produce a dynamic model of forest growth, a model in which changes in the state of the forest are a function of the present state and random components. This approach has two advantages over the curve-fitting approach to forest growth: first, the simulator can be regarded as a repository for an integrated knowledge of the ecosystem; second, additional hypotheses can be formulated and tested using Monte Carlo samples of simulator runs and comparing the results with observed data. For

Rationale, Limitations, and Assumptions of a Northeastern Forest Growth Simulator

A cooperative agreement between Yale University and the 1970 summer program of the IBM Research Division resulted in a flexible computer program to simulate the growth of the uneven-aged, mixed-species stands of trees on the 10-meter by 10-meter experimental plots of the Hubbard Brook Ecosystem Study in the White Mountains of northern New Hampshire. Annual increments of tree growth are based on species, tree size, and allocation of available light among the competing trees of the plot. Site quality differences between plots are assigned primarily by the concept of tree-growing degree-days, although soil moisture storage during the growing season and plot rockiness are also considered. Species succession, individual tree suppression and release, and other dynamic properties of forest stands have been successfully reproduced using the program. Additional field measurements are needed to further verify the model and to extend its applicability to nutrient cycling and other aspects of the Hubbard Brook Ecosystem Study. We believe that the simulator could readily be extended to include most other tree species of northeastern North America and also to match data from other sites through appropriate adjustment of program parameters.